Attachment-driven morphology evolvement of rectangular ZnO nanowires

The rectangular cross-sectional ZnO nanowires were synthesized in a solution method. An attachment-driven growth mechanism was proposed for the morphology evolvement of ZnO nanocrystals from nanoparticles to nanoplates and eventually to nanowires. Due to the pileup attachment of the nanoplates to recrystallize into nanowires, unique one-dimensional (1D) ZnO nanowires with the rectangular cross section were obtained, which is different from those nanowires in the previous reports. It is the first time the evidence that "oriented attachment" can occur not only for nanoparticles but also for nanoplates was obtained, suggesting that "oriented attachment" is an intrinsic behavior for nanosized materials. According to the growth model proposed based on the direct TEM observations, ZnO nanocrystals can be easily controlled as nanoparticles, nanoplates, or nanowires by tuning the synthetic parameters.     

Influence on electrochemical impedance and photovoltaic performance of natural DSSC using Terminalia catappa based on Mg-doped ZnO photoanode

In this paper, we report the successful fabrication of a novel dye-sensitized solar cell (DSSCs) using Mg doped ZnO as photoanode and natural dye Terminalia catappa as sensitizer. We synthesized Mg doped ZnO nanoparticles at different Mg concentrations (2%, 4%, 6%, and 8%) by employing a simple solvothermal route. The structural, morphology, composition and optical investigations of synthesized Mg doped ZnO nanoparticles are carried out using XRD, FE-SEM, EDAX, TEM, SAED, FTIR and UV–visible measurements. The XRD results confirmed the formation of hexagonal-wurtzite structure for the Mg doped ZnO nanoparticles and increase of crystalline size with increasing dopant concentration up to 6% is observed. FESEM analysis indicated a gradual change in the surface morphology with increasing Mg concentration and the size of the nanoparticles are slightly reduced at higher Mg concentration. The HRTEM images and SAED pattern also confirmed the formation of wurtzite hexagonal phase of ZnO. The band gap energies calculated from the UV–visible spectra using Tauc's plots indicated decrease of band gap energy with dopant concentration. The DSSCs fabricated using Mg doped ZnO photo-anodes and Terminalia catappa sensitizer showed higher efficiency at higher Mg concentration and observed increase in efficiency is discussed based on slower charge carrier recombination and higher carrier life time as evidenced from the electrochemical impedance analysis.     

Novel Green Route of Synthesis of ZnO Nanoparticles by Using Natural Biodegradable Polymer and Its Application as a Catalyst for Oxidation of Aldehydes

ZnO nanoparticles have been synthesized by using biodegradable natural biopolymer viz. Gum Tragacanth. This single step approach is very cost effective and reproducible. The reaction time and concentration of precursor zinc acetate play a major role in the nature and growth of ZnO nanoparticles. ZnO nanoparticles were characterized by X-ray diffraction, SEM, FTIR, EDAX, UV-visible spectroscopy and TEM. ZnO nanoparticles with 20-30 nm in diameter and hexagonal morphology were found; dispersed uniformly. Raman spectrum shows the mode E₂ high at 437 cm^?1 that is related to the vibration of wurtzite Zn-O bond in crystal structure of ZnO. The space between adjacent lattice fringes is ～ sharp 2.42 Å. UV-visible absorption spectrum shows the sharp absorption band at 308 nm assigned to the intrinsic transition from valance band to conduction band. The ZnO nanoparticles display superior catalytic activity of conversion of aldehyde to acid as compared to bulk-ZnO material, because of high surface area of ZnO nanoparticles. A trace amount of ZnO nanoparticles catalyst required for organic conversion. The ZnO nanoparticles as catalyst are highly stable, recyclable and efficient in its activity.     

Spherical Zinc Oxide Nano Particles from Zinc Acetate in the Precipitation Method

The liquid precipitation method using zinc acetate dihydrate was applied for the synthesis of uniform and spherical ZnO nanoparticles. The ultrafine zinc oxid was prepared in a water‐ethanol mixture solution. The solution containing zinc cation was soluble in water. The surface‐active agent triethanolamine (TEA) was soluble in ethanol. Then alkali precipitated by adding n‐propylamine. The spherical zinc oxide particle morphology was found to be highly dependent on the zinc salt concentration, ethanol‐water ratio, and the surface‐active agent additive. The process can produce white ZnO powder of 50–90 nm in size. The morphology of zinc oxide showed a powder shape by transmission electron microscopy (TEM), the crystallization phase structure of zinc oxide by X‐ray diffraction (XRD), and the zinc oxide remaining by using an organic analysis by infrared spectroscopy (IR).     

Synthesis of CuS and ZnO/Zn(OH)2 nanoparticles and their evaluation for in vitro antibacterial and antifungal activities

In this study, the copper sulfide nanoparticles (CuS‐NPs) and the zinc oxide/zinc hydroxide nanoparticles ((ZnO/Zn(OH)₂‐NPs) were synthesized by a simple and low‐cost method, and the synthesized nanoparticles were characterized and identified by UV–Vis, field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The antimicrobial activity of the CuS‐NPs and the ZnO/Zn(OH)₂‐NPs were examined by broth dilution to determine the minimal inhibitory concentration (MIC) of antibacterial agent required to inhibit the growth of a pathogen and the minimum bactericidal concentration (MBC) required to kill a particular bacterium. Agar disc diffusion method was used to determine the zone of inhibition. The nanoparticles demonstrated potent antibacterial activity against Klebsiella pneumonia (ATCC 1827), Acinetobacter baumannii (ATCC 150504), Escherichia coli (ATCC 33218) and Staphylococcus aureus (ATCC 25293). Antifungal activity against Aspergillus oryzae (PTCC 5164) was also obtained. The data obtained from antimicrobial activities by broth dilution and agar disc diffusion methods exhibited the CuS‐NPs were more effective than the ZnO/Zn(OH)₂‐NPs. A good correlation was observed between the data obtained by both methods.     

Single‐Crystalline ZnO Nanowire Bundles: Synthesis,Mechanism and Their Application in Dielectric Composites

Single‐crystalline ZnO nanowire bundles have been synthesized in large‐scale by an improved microemulsion method in the presence of excessive hydrate hydrazine and dodecyl benzene sulfonic acid sodium salt (DBS) in xylene. The product is characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy (HRTEM). The result shows that the bundle is composed by many oriented single‐crystalline ZnO nanowires with a length of about 1 μm and a diameter of about 20–30 nm. The influence of DBS, hydrazine and the reaction time on the morphology of final product and the formation mechanism of such nanostructures were discussed; the application in the dielectric composites is also studied.     

The synthesis and optical properties of the heterostructured ZnO/Au nanocomposites

ZnO/Au heterostructured nanoparticles were formed through epitaxial growth of Au on the ZnO seeds. The morphology and structure of ZnO/Au nanocomposites were investigated by TEM and XRD analysis. The nanocontact between Au and ZnO results in red-shift of surface plasmon of the Au and increase the intensity of Raman signals of ZnO. Heterostructured ZnO/Au nanocomposites also enhance chemical stability of ZnO in aqueous solution.     

Influence of different substrates on ZnO nanorod arrays properties

Zinc Oxide (ZnO) nanorod arrays were grown on different substrates by hydrothermal method. The crystallinity of ZnO nanorod was regularly investigated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine morphology of the ZnO nanorods. The results indicate that the nanorods grow along [002] orientation. SEM and TEM images and XRD patterns show that the growth of ZnO nanorods on graphene/Quartz substrate is better than the other substrates due to the number and size of the nanorods which are highly affected through the properties of ZnO seed layers and it has lower defects than the other substrates. PL spectra ZnO would have a higher concentration of oxygen vacancy.     

Preparation of polymer hollow microspheres covered by polymer solid particles via two polymerization steps

A novel surface modification method for titania nanoparticles is provided via the surface‐initiated photocatalytic polymerization with the aid of acrylic acid (AA) or sodium styrene sulfonate (NaSS). The properties of modified titania nanoparticles are investigated with aqueous electrophoresis measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Then the modified titania is used as Pickering stabilizer for further polymerization and the morphology of the resulted polymer microspheres is characterized by TEM and field‐emission scanning electron microscopy. It is proven that the addition of AA or NaSS for the surface‐initiated polymerization can obviously affect the structure and morphology of the final polymer composite microspheres. The formation mechanism of several kinds of polymer particles is also proposed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

离子液体中ZnO纳米棒的制备与表征

离子液体中ZnO纳米棒的制备与表征;离子液体;ZnO纳米棒;热分解     

Hydrothermal growth of well-aligned ZnO nanorod arrays: Dependence of morphology and alignment ordering upon preparing conditions

Well-aligned ZnO nanorod arrays were prepared on substrates by hydrothermal growth under different conditions. The effect of preparing conditions on the deposition of ZnO nanorods was systematically studied by scanning electron microscopy, X-ray diffraction and photoluminescence spectroscopy. It is demonstrated that the growth conditions such as pre-treatment of the substrates, growth temperature, deposition time and the concentration of the precursors have great influence on the morphology and the alignment ordering of ZnO nanorod arrays. Pre-treatment of substrates, including dispersion of ZnO nanoparticles and subsequent annealing, not only plays a main role in governing the rod diameter, but also greatly improves the rod orientation. Although the rod diameter and its distribution are mainly determined by pre-coated ZnO nanoparticles, they can also be monitored to some extent by changing the concentration of the precursors. The growth temperature has a little influence on the orientation of nanorods but it has great impact on their aspect ratio and the photoluminescent property. Kinetic studies show that the growth of ZnO nanorods contains two distinct step: a fast steps within the first hour, in which the nanorods tend to be short and wide, and a slow step, in which long rods with high aspect ratio are obtained.     

Tuning the aspect ratio of hydrothermally grown ZnO by choice of precursor

Variable aspect ratio (length/diameter), one dimensional ZnO nanostructures are synthesized by reacting Zn²⁺ precursor derived from Zn·Ac₂, Zn·Cl₂ and Zn·(NO₃)₂ under hydrothermal treatment. The growth mechanism illustrating the formation of self-assembling from individual ZnO nanoparticles to rod-like form is explained briefly. XRD reveals that the ZnO obtained from various zinc salts are pure, wurtzite structure, with crystalline hexagonal phase. The qualitative analysis of ZnO formation and morphology of ZnO nanoparticles are estimated from FESEM and TEM micrographs. Strong UV absorption corresponding to the recombination of electron-hole pair is observed and the blue shift absorption obeys the size confinement effect. The extent of absorption relatively varies when the morphology is changed from nano-bundles to individual rod-like ZnO. When electrons are excited at wavelength of 240 nm, a strong near band edge (NBE) emission and surface defects emission are observed in the PL spectra. The broader emission situated in the blue-green region of the visible spectrum, originating from surface oxygen defects, is not observed in ZnO derived from Zn·Ac₂.     

不同形貌ZnO纳米粒子的超声化学法制备与表征

One-dimensional ZnO nanorods and shuttle-like ZnO nanoparticles have been successfully achieved by ultrasonic irradiation of Zn (CH3COO)2 aqueous solution and Zn-NH3 complexcs solution. The obtained ZnO nanoparticles have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electronic diffraction (SAED). And the formative mechanism of the prepared different morphological ZnO nanoparticles is also discussed under ultrasonic irradiation.     

Controlled fabrication of highly oriented ZnO microrod/microtube arrays on a zinc substrate and their photoluminescence properties

Well-aligned zinc oxide microrod and microtube arrays with high aspect ratios were fabricated on zinc foil by a simple solution-phase approach in an aqueous solution of ethylenediamine (en). The shape of the ZnO microstructures can be easily modulated from rods to tubes by adding cetyl trimethyl ammonium bromide (CTAB) into the reaction system. Control experiments demonstrate that some reaction parameters, such as the concentration of ethylenediamine, the kind of surfactant, reaction time, and the temperature, all have direct influences on the morphology of the products. Based on the early structure arising from arrested growth (nanosheets), a reasonable mechanism for the growth of ZnO microrods and microtubes has been proposed. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence emission.     

Preparation and application of polystyrene‐grafted ZnO nanoparticles

The precursor of ZnO was prepared by precipitation and ZnO nanoparticles were obtained by calcination afterwards. Poly(styrene) (PSt) was grafted onto the ZnO nanoparticles in a non‐aqueous suspension to reduce the aggregation among nanoparticles and to improve the compatibility between nanoparticles and the organic matter. The obtained samples were characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT‐IR), zeta potential measurement, lipophilic degree (LD) test, photocatalytic experiments, sedimentation test, and contact angle measurement. The LD of composite particles after a high‐temperature treatment was stable. The photoluminescence of PSt‐grafted ZnO nanoparticles was observed by naked eyes and was recorded using a digital camera. The ZnO nanoparticles were used to reinforce poly(vinylidene fluoride) (PVDF) films and the mechanical and electric properties of the films were also measured. Copyright © 2007 John Wiley & Sons, Ltd.     

PEG辅助氧化锌纳米棒的水热法制备

采用PEG辅助水热法合成了ZnO纳米棒,XRD显示产物为结晶良好的六角结构晶体ZnO,PL谱表明适当退火处理后产物有较好的光致发光性能.利用TEM和SAED研究了纳米棒的形貌和生长机制,并研究了氢氧化钠浓度和反应时间对产物形态和尺寸的影响.     

Preparation and Photoluminescence of ZnO Comb-Like Structure and Nanorod Arrays

A large quantity of Zinc oxide (ZnO) comb-like structure and high-density well-aligned ZnO nanorod arrays were prepared on silicon substrate via thermal evaporation process without any catalyst. The morphology, growth mechanism, and optical properties of the both structures were investigated using XRD, SEM, TEM and PL. The resulting comb-teeth, with a diameter about 20 nm, growing along the 0001 direction have a well-defined epitaxial relationship with the comb ribbon. The ZnO nanorod arrays have a diameter about 200 nm and length up to several micrometers growing approximately vertical to the Si substrate. A ZnO film was obtained before the nanorods growth. A growth model is proposed for interpreting the growth mechanism of comb-like zigzag-notch nanostructure. Room temperature photoluminescence measurements under excitation wavelength of 325 nm showed that the ZnO comb-like nanostructure has a weak UV emission at around 384 nm and a strong green emission around 491 nm, which correspond to a near band-edge transition and the singly ionized oxygen vacancy, respectively. In contrast, a strong and sharp UV peak and a weak green peak was obtained from the ZnO nanorod arrays.     

Biosynthesis of ZnO nanoparticles through extract from Prosopis juliflora plant leaf: Antibacterial activities and a new approach by rust-induced photocatalysis

Rust-induced photocatalytic and antibacterial activities of ZnO nanoparticles derived from Prosopis juliflora leaf extracts by biosynthesis using the hydrothermal method at 170 °C are reported in this study. The characterization has been accomplished by various methods such as XRD, DRS, FT-IR, SEM, TEM, EDAX, and PL spectra. XRD exhibits that ZnO has a hexagonal wurtzite structure with a preferred orientation of 101 planes. The functional groups, which are present in the leaf extracts, are responsible for corresponding peaks in FT-IR spectra. The FESEM images of the synthesized nanoparticles show the morphology sphere like structure. ZnO particle size of 65 nm has been observed from HR-TEM analysis. The elemental composition has a good agreement with the biosynthesized ZnO nanoparticles. The antibacterial activities have been carried out in vitro assays against four different pathogens viz Escherichia coli (E. coli), Rhodococcus rhodochrous (R. rhodochrous), Bacillus subtilis (B. subtilis) and Vibrio cholera (V. Cholera) against a standard (streptomycin sulfate). Furthermore, the Photocatalytic ability of the titled nanoparticles has been experimented from the rust solution with methylene blue and degradation under UV radiation of 99%. The proposed mechanism is based on scavenger studies and it is investigated during the photo degradation of Methylene blue. The catalytic amount and recovery of photocatalyst have also been studied in detail.     

Ultrasonic treatment as recent and environmentally friendly route for the synthesis and characterization of polymer nanocomposite having PVA and biosafe BSA‐modified ZnO nanoparticles

The present study deals with the immobilization of ZnO nanoparticles (NPs) as nanofiller inside poly(vinyl alcohol) (PVA) by solution casting method which is a low‐cost, environmental‐friendly, and rapid method of sonochemistry. Firstly, the surface of ZnO NPs was treated by bovine serum albumin (BSA) in the phosphate‐buffered solution under ultrasonic cavitation. Three diverse polymeric nanocomposites (NCs) are formed by changing the percentage of ZnO@BSA NPs (3, 6, and 9 wt%) with same amount of PVA. The structure properties, morphology, and thermal stability of prepared NCs were determined through Fourier transform‐infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy (EDX) and optical UV‐Visible spectrum, transmission electron microscopy (TEM), and field emission scanning electron microscopy. The presence and the dispersal of the ZnO@BSA NPs in the PVA matrix were recognized by TEM. In the X‐ray diffraction analysis, the values of mean particle size using Debye‐Scherrer equation were estimated in the range 4 to 6 nm that is almost in agreement with TEM analysis. Increase of 14% in thermal stability and also increase of more than 2‐fold of the tensile strength of PVA/ZnO@BSA NC 9 wt% in respect to the pure PVA showed that the modified NPs well dispersed within PVA and attached to it.     

Enhanced Visible Light Irradiation Photocatalytic Performance of MgFe2O4 After Growing with ZnO Nanoshell and Silver Nanoparticles

MgFe₂O₄ implanted with ZnO and silver nanoparticles has been successfully synthesized. The formation mechanism of the core~shell structured Ag/ZnO /MgFe₂O₄ nanoparticles was investigated. The efficacy of degradation of an organic dye was compared under the visible light irradiation with the individual components (MgFe₂O₄ , ZnO , and Ag). The structure of Ag/ZnO /MgFe₂O₄ nanoparticles was established from detailed structural analyses using a vibrating‐sample magnetometer (VSM), X‐ray diffraction (XRD ), selected area electron diffraction (SAED ), scanning electron microscopy (SEM ), energy‐dispersive X‐ray spectroscopy (EDS ), and transmission electron microscopy (TEM ). Ag/ZnO /MgFe₂O₄ nanoparticles showed a saturation magnetization (M _s) of 44 emu/g. It is seen from the results that ZnO is coated on the surface of MgFe₂O₄ nanoparticles, and Ag nanoparticles are attached to the edge of the ZnO /MgFe₂O₄ nanoparticles. In addition, the nanoparticles were found to be spherical with appropriate structures. The electron transfer mechanism greatly enhances the rhodamine B (RhB ) degradation rate, which is illustrated and discussed in detail. The obtained Ag/ZnO /MgFe₂O₄ nanoparticles were photostable and magnetically recyclable with potential application in the degradation of organic pollutants.